Answer:
Demonology is the study of demons. Christian demonology is the study of what the Bible teaches about demons. Closely related to angelology, Christian demonology teaches us about the demons, what they are and how they attack us. Satan and his demons are fallen angels, real personal beings who wage war against God, the holy angels, and humanity. Christian demonology helps us to be aware of Satan, his minions, and their evil schemes. Here are some important issues in Christian demonology:

What does the Bible say about demons? The Bible indicates that the demons are fallen angels – angels who along with Satan rebelled against God. Satan and his demons now desire to deceive and destroy all those who follow and worship God.

How, why, and when did Satan fall from heaven? Satan fell from heaven because of the sin of pride, which led to his rebellion against God. The actual time of his fall is not recorded in Scripture. It may have occurred outside time as we know it, that is, before the creation of time and space.

Why did God allow some of the angels to sin? The angels who fell and became demons had a free-will choice to make – God did not force or encourage any of the angels to sin. They sinned of their own free will and therefore are worthy of God's eternal wrath.

Can Christians be demon possessed? We strongly hold to the belief that a Christian cannot be possessed by a demon. We believe there is a difference between being possessed by a demon, and being oppressed or influenced by a demon.

Is there activity of demonic spirits in the world today? Considering the fact that Satan "walks about like a roaring lion, seeking whom he may devour" (1 Peter 5:8) and knowing that he is not omnipresent, it is logical to assume that he would send his demons to do his work in this world.

Who or what were the Nephilim? The Nephilim ("fallen ones, giants") were the offspring of sexual relationships between the sons of God and daughters of men in Genesis 6:1-4. There is much debate over the identity of the "sons of God."

Many people believe Satan and his demons are only personifications of evil. Christian demonology helps us to understand the nature of our spiritual enemy. It teaches us how to resist and overcome the devil and his temptations. Praise God for the victory over darkness through our Lord Jesus Christ! While the Christian should not be obsessed with demonology, a clear understanding of demonology will help calm our fears, keep us watchful, and remind us to stay close to our Lord Jesus Christ. We have the Holy Spirit living in our hearts, and "greater is He that is in us than he that is in the world" (1 John 4:4).

A key Scripture related to Christian demonology is 2 Corinthians 11:14-15, "And no wonder, for Satan himself masquerades as an angel of light. It is not surprising, then, if his servants masquerade as servants of righteousness. Their end will be what their actions deserve."